CA1039781A - Multi-chamber arc quenching device with nozzle-chaped contacts - Google Patents
Multi-chamber arc quenching device with nozzle-chaped contactsInfo
- Publication number
- CA1039781A CA1039781A CA204,921A CA204921A CA1039781A CA 1039781 A CA1039781 A CA 1039781A CA 204921 A CA204921 A CA 204921A CA 1039781 A CA1039781 A CA 1039781A
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- arc
- nozzle
- chamber
- electrodes
- quenching
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Abstract
A B S T R A C T
An improved method for quenching an arc in an AC circuit breaker having an arc chamber in which the arc rotates in a quenching medium between open electrodes having ends close together in which the arc is caused to generate during its rotation, through a heating of the quenching medium, an over-pressure which is maintained beyond the zero crossing of the AC current with the gas flow produced by the over-pressure used for blasting the arc in the nozzle. Various embodiments for use in medium and high voltage switching installations which permit the switching of large currents with a simple and inexpensive arrangement are illustrated.
An improved method for quenching an arc in an AC circuit breaker having an arc chamber in which the arc rotates in a quenching medium between open electrodes having ends close together in which the arc is caused to generate during its rotation, through a heating of the quenching medium, an over-pressure which is maintained beyond the zero crossing of the AC current with the gas flow produced by the over-pressure used for blasting the arc in the nozzle. Various embodiments for use in medium and high voltage switching installations which permit the switching of large currents with a simple and inexpensive arrangement are illustrated.
Description
1~)3978~ 1 :
This inYention relates to a method of quenching an arc in an alternating current circuit breaker having an arc chamber in which the rotating arc is blasted by a quenching medium. Circuit breakers of this kind are pre~
ferably used in medium- and high-tension plants, in particular carrying a supply voltage exceeding 1000 V.
It is generally known that medium- and high-tension circuit breakers for alternating current extinguish at the zero-crossing point of the current. In a compressed gas circuit breaker a locally restricted circuit-breaking arc is subjected to the flow of a quenching gas, whereas in a circuit breaker with a rotating arc the arc is quenched by imparting to it a rapid movement in a stationary gas, prefer-ably a quenching gas, in particular sulfur hexafluoride SF6.
Circuit breakers with a rotating arc do not require pressure .. .. .
gradient in the quenching gas, German Patent 646,031 discloses the quenching of an arc which rotates in a quenching medium inside an arc chamber. The arc is driven by an electromagnetic field into ;
, 20 a pressurized flow of a quenching medium flowing out of the J
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~39~81 chamber and the arc is rotated in this flowing medium by means of another electromagnetic field. One of the low ends of the arc is driven by the electrodynamic effect of a current loop into a tubular contact. The arc is rotated inside that tube and blasted by the flowing quench- -ing mediu~. The cross-section of the flow, defined by the internal width of the tubular contact must, therefore, be of a magnitude sufficient to permit rotation of the arc within the opening.
Although these prior art methodsand apparatus work reasonably well, there is a need for improved methods :
of arc quenching due to various deficiencies. Prior to summarizing the present invention, a discussion of the oper- .
ation of gas flow breakers which operation is helpful in un-derstanding the present invention will be given. - :' -In what are referred to as gas flow breakers, i,e., high capacity circuit breakers using flowing gas as a quenching medium, in which the arc burns in nozzle arrange-ments, the switching capacity is heavily influenced by what '~
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1~39781 is referred to as back-up effect. Back-up effect is a certain interaction between the quenching gas flow and the arc. In a gas flow breaker the arc burns between two contacts, at least one of which is generally shaped as a tubular contact and forms at the same time a nozzle for thé gas flow. However, it is also possible for the contacts to be preceded by a separate nozzle.
The ~asic characteristic of all these arrangements is that the arc must burn through a hollow space. The hollow space may be cylindrical, conical or Laval-tube shape and may be of different length. The quenching medium must flow through this hollow space forming the nozzle or acting as a nozzle. The quenching medium flow will be impeded by an arc therein. Using simple model concepts, two zones can be distinguished within the nozzle, and inner hot zone with low density and an outer cold zone with high density. The inner zone is formed by the arc while the major portion of the total mass passing through the nozzle flows through the outer cold zone. The thicker tha arc becomes, the wider the hot zone becomes. This happens at the expense of the cold outer zone. As a result, with increasing arc thickness, the mass flow through the nozzle teclines. If the arc completely fills the nozzle cross-section, mass ; flow is minimal.
,~ , Thus, flow resistance in the nozzle increases as a function of the power of the arc. At the same time, the mass flow through the nozzle decreases :t ~ .
~ as a function of the temperature. The removal of the gas heated in the quench-`t~. ing chamber for the duration of the arc requires a certain amount of time, ~ ~ ~ particularly where large currents are being switched. Furthermore, the gas 3 flow adjusts itself only subsequently with a time delay because of the mass inertia. In an AC circuit breaker, the arc current varies in accordance with the sinusoidal waveform of the current half-waves. In interrupting a large current, particularly a short-circuit current, the effects mentioned above occur in the vicinity of the current maximum.
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With increasing cooling-down of the arc, a radial gas flow inward occurs and thereby a corresponding increase in density. An additional annular _ . ,~ : .
1~39781 c~oss sectlon is thus m~de aYailable fo~ the gas flow. At the zero crossing of the current, the undlsturbed steady~state flow which depends only on the pressure is not yet reestablished but is reduced by a predetermined amount. This flow reduction impedes the cooling of the arc and the development of a temper-ature distribution favorable for quenching at the important time interval just prior to the zero crossing.
The reduced cooling effect in dependence on the decreasing mass flow has a consequence that the power released in the quenching chamber cannot be removed by the quenching medium. One result of this is a large pressure increase in the quenching chamber. The pressure increase can lead not only to a reduction of the inflow from the high-pressure part of the circuit breaker, but even to a reversal of the flow direc-.
tion. Through such a reverse flow, hot gas can get into the supply canals. If with a then decreasing magnitude of the current, the gas flow resumes in the desired direction, quenching medium which has already been heated and which may be contamin-ated with metal vapor from the electrodes flows first into the 2Q quenching arrangement. Because of these effects, designs which largely suppress the back-up effect using the special measures ;
have been developed. Typical are the measured disclosed in the document ETZ-A, vol. 90, no. 26, pages 711 to 714 tl969) where ETZ is an abbreviation of Elektro-technische Zeitung).
~ In gas flow breakers, the back-up effect is prevented primarily y .~ .
!: ~4~ ~-by making the discharge openings of the nozzles relatlvely large, in accordance with the power to be interrupted The back-up effect which occurs in conjunction with the known quenching of an arc by rotation between elec-trodes arranged parallel to each other can lead to a particular-ly advantageous quenching effect. Thus, the present invention essentially comprises using the arc to generate during its rotation an overpressure due to heating of the quenching --medium which is maintained beyond the zero crossing of the AC current and which thereby results in a gas flow of the quenching medium which is used for blasting the arc in a nozzle. With the method of the present invention, a back-up effect is thus generated in order to bring about, during the current half-wave, a pressure build-up in the arc chamber, which then results in a flow of the quenching medium through the nozzles.
Contrary to the known gas flow breakers, intensive I flow cooling is achieved only in the immediate vicinity of ! the time of the current zero crossing, i.e., only at that , 20 time is the arc in the vicinity of the nozzle. It has i - .. .
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been d~scovered that it is adYantageous that the arc be cooled as little as poss~le during the rotation phase, in ~ ;
order to keep the power conYersion as low as possible. For this reason, particularly fast rotation is not required. ;
The rotation of the arc is used primarily to reduce burn-off of the electrodes and to heat the quenching medium in the arc chamber as uniformly as possible. -When the current is being switched off, the arc can be drawn from one electrode to the other in a simple fashion using a switching bar, which in the closed condition protrudes through the nozzles disposed opposite each other in the arc quenching chamber. Thus, a switching rod movable in its ~;
length-wise direction is provided for operating the breaker.
Similarly, a switching tube may also be used. ~or establish-ing good contact, at least one of the nozzles can be equipped ~ with spring contacts or a pressure contact device of well ¦~ ~ known design.
¦~ In some cases, a single equalization chamber arranged ¦ ~ above or below a cylindrical arc-quenching chamber may be ¦~ 20 suficient, In such an arrangement, quenching gas 10ws from one side of the chamber through a nozzle and the arc is accord-ingly influenced by the flow only on one side. With such an arrangement of the switching apparatus, the end of the other electrode opposite the nozzle can advantageously be provided ` ~ with a pressure or finger contact arrangement of known design.
The end of the switching rod is then connected with this contact arrangement when the breaker is closed. The switching~tube or rod movably arranged in one or two nozzles ;
` ~ ~ can additionally be guided b~ a sliding contact disposed in the 30- equalizatlon chamber. In an arrangement where two equalization ~6 ~ r ~1)39781 ~
chambers are used, such a sliding contact can further be provided in addition to the second equalization chamber.
According to a broad aspect of the present invention there is pro- ~-vided apparatus for quenching a rotating electric AC arc of high current intensity having an arc chamber wherein the arc heats a quenching medium which is adapted to flow off at a predetermined over-pressure through at least one opening in an equalization chamber, characterized in that the open-ing has the configuration of a nozzle disposed in such a fashion that at least during the quenching phase the arc fires through this nozzle and in that the dimensions of the nozzle are selected in such a manner that the ~
over-pressure produced in the arc chamber is maintained beyond the zero ~;
passage of the AC current.
In a disclosed embodiment of the invention, electrodes which con-tain discharge nozzles in several places for conducting the quenching medium from the arc chamber to the equalization chamber are provided. The addition-al nozzles are disposed at points of the electrodes where it can be expected that the base points of the arc will remain stationary for small magnitudes of the current due to the greater curvature or an insulating interruption.
In such a case, the magnetic driving forces will no longer be sufficient to move the base points away from these electrode parts. The sum of the inside nozzle cross sections is chosen such that the back-up effect, which is ad-vantageous for the generation of the flow, can still take place.
In each of the disclosed arrangements, it is advantageous to embed the electrotes of conductive material along with at least one nozzle in slots of insulating plates or walls of the arc chamber. This prevents the highly curved, voltage-carrying edges from projecting into the arc chamber a~d improves the dielectric strength of the chamber considerably.
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In the equalization chambers, additional magnetic blasting coils ~"~ will preferably be provided. The blasting coils are connected to the elec-trodes and their current leads -~ .. . . .
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1~J39781 in such a manner that they are bridged, i.e., electrically , shorted, by the switching rod or the switching tube when the breaker is closed. Thus, they a~re in the circuit only during the switching process. ~he blasting coils may further be associatPd with at least one shorted turn which produces a phase shift of the magnetic field with respect ;
to the arc current. As a result, the driYing force acting on the arc current will remain relatively large even shortly prior to the zero crossing of the current.
For limiting the current, electric resistors which are switched into the circuit upon operation of the breaker and thereby limit the current to be interrupted, e.g., a short-circuit current, to a low Yalue can be included ;
in the equalization chambers in addition to or instead of ~ the coils.
j A particular adYantage of the apparatus disclosed is that seYeral switching deYices can be connected in series in a simplb manner with a common driYe associated with the switching rod of the indiyidual switchiDg deYices.
~ 20 In addition to a gaseous quenching medium such I as sulfur hexafluoride, the quenching device according to ,1 .
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1~39781 the present invention can al50 be operated with a liquid quench-ing medium such as oil. In such an embodiment, the oil evapor-ates due to the arc and the oil vapor is used for blasting at least one of the arc bases. In such a case, it i5 advantageous to provide the equalization chambers with val~es which allow the decomposition products to discha~ge to the outside.
A particularly advantageous embodiment of the quench-ing arrangement using a liquid quenching medium is obtained through the use of liquid sulfur hexafluoride SF6. Liquid SF
has a vapor pressure of 21 atmg at 20C and still about 5.1 atm abs at -30C. Thus, at normal ambient temperature, e.g., between 0 and 30C, an SF~ gas atmosphere of 13 to 27 atm abs in a switching chamber partially filled wi~h liquid sulfur hexa-fluoride SF6 is present. This causes a substantial increase of the dielectric strength as compared to a breaker operated only with a pure SP6 gas atmosphere of about 5 to 7 atm abs.
Since the decomposition products of sulfur hexafluoride recom-bine to again form sulfur hexafluoride upon cooling down, a discharge of the decomposition products to the outside is not necessary where this is used as the quenching medium. This is a great advantage, particularly for an installation in an encapsulated system.
Figure 1 is a cross-sectional view of a first ~ embodiment of a quenching arrangement having two equalization ¦ chambers.
~,~ Figure 2 is a plan view partially in cross-section I illustrating a type of electrode which can be used in the `1 ' .
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1~39781 : ~:
embodiment of Figure 1.
Figure 3 is a perspective view illustrating current flow through the electrode of Figure 2 and the magnetic -fields generated thereby. -~
Figure 4 is a cross-sectional view of a nozzle electrode of Figure 1 illustrating current flow therethrough.
Figure 5 is a plan view illustrating another type ~ -~
of electrode which may be used.
Figure 6 illustrates a still further type of elec-trode.
Figure 7 is a similar view of an arrangement with a single equalization chamber which arrangement is particularly adapted for use with a liquid quenching medium.
A first embodiment of a quenching arrangement for carrying out the method of the present invention is illustrated on Figure 1. An essentially cylindrically shaped member 8 ; having a top cover 14 is provided. Centrally located within this cylindrical structure is a quenching chamber 2 defined by a top partition 4 and a bottom partition 6 along with the ;
cylindrical side walls of the cylindrical member 8. The space ;
between the partition 4 and the top 14 forms a first equaliza-tion chamber. A partition 16 along with the partition 6 forms a second equalization chamber 12. As illustrated, the equaliz-;~ ation chamber 10 is above the quenching chamber 2 and the equalization chamber 12 below the quenching chamber 2 The ~ walls of the chambers including the cylindrical wall 8, the ~~ .
~ top 14, bottom 16 and partitions 4 and 6 may advantageously .~
~; be made of a-heat resistant insulating material, such as ceramic or -,; :'.. . :, '~
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1039781 ~
plastic. At the inside surface of the partition 4 of the arc chamber 2 and at its bottom partition 6, also on the inside, are arranged re~pective elec-trodes 20 and 22. One end of the electrode 20 is connected with an electri-cal lead 24 and one end of the electrode 22 with an electrical lead 26. The other end of the electrode 20 is designed as a nozzle 28 and that of the electrode 22 as a nozzle 30. The nozzles 28 and 30 form respective openings in the partitions 4 and 6. A switching rod 32 having an outside diameter matching the inside diameter of nozzles 28 and 30, protrudes through both nozzles, establishing the electrical connection between the electrodes 20 and 22. The switching rod can be moved along its axis by a drive, not shown. It is brought through a corresponding opening in the bottom 16 of the lower equalization chamber 12 and will preferably be guided in an additional sliding contact 34 arranged at the bottom partition 16. As shown, it can be electri-cally connected with the lead 26 along with being connected to a current sup-ply line 36. The two equalization chambers 10 and 12 can also have therein a magnet coil. Shown is a magnet coil 38 in chamber 10 and a magnet coil 40 in chamber 12. These produce a magnetic blasting field for the arc which is drawn between the electrodes 20 and 22 using the switching rod 32. The blast-I ing coils 38 and 40, whose electrical conductor connections are not shown in t 20 the figure, are connected electrically in series and in magnetic opposition.
At least one short-circuited turn, also not shown on the figure, can be i~
~ associated with each of the blasting coils 38 and 40 to cause, in a well known ~ fashion, a phase shift of the magnetic field of the blasting coil with res-pect to the arc current producing the field. These short-circuit turns may be arranged, for example, directly at the coils 38 and 40 or may partially sur-round the coils. With such an arrangement, they will have a particularly close coupling with the coils.
~etween the arc chamber 2 and the equalization chambers 10 and 12, tl~ respective chec~ valves 18 and 19 are provided. These are adjusted so that ' 30 they open only upon exceeding a predetermined maximum pressure in the arc .~. ' . ' , .
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chamber 2. They thereby make possible a reduction of the pressure by providing openings in addition to the nozzles. Also shown on Figure 1 are safety valves 37 and 39 in the wall 8 at the chambers 10 and 12 respectively. These safety valves which vent to the outside are set to a predetermined maximum pressure and may, for exampleJ be spring valves or burst diaphragms. These safety devices prevent an explosion of the switching device if the current being in-terrupted assumes values which cannot be interrupted by the circuit breaker.
Either one or both of the safety valves 37 and 39 may be advantageously in-cluded.
As is evident from the cross-sectional plan view through the arc chamber 2 as shown on Figure 2, the electrode 20 is an open ring electrode which has an approximately uniform distance from the chamber wall 8 and whose ends A and C form an opening B in the ring. The end C has a larger cross section with its inner opening 29 forming the nozzle whose cross-sectional profile is laid out for aerodynamic acceleration and preferably may have the profile of a Laval tube.
During a half-wave of the operating current, which as illustrated on Figure 3, flows through the lead 26 along with electrode 22 in the direction indicated by the arrow, an arc E is drawn between the ends C of the electrodes -- 20 and 22 as the switching rod 32 is moved downward~ In the electrode 20, the current flows in the opposite direction, also as indicated by arrows on Figure 3, and leaves the quenching arrangement through the lead 24.
With the directions of current indicated, the two ring-shaped electrodes 20 and 22 form what is referred to as a cusp field designated by 42 and 44 and shown in dot-dash lines on the figure. The cusp field has a rad-ial component which generates a force K acting on the arc E in the tangential direction in the space between the electrodes 20 and 22. The arc is also ! ~ driven by the action of its own electromagnetic force. The latter is produced by the loop formation of the electrode parts adjacent to the ends C with the arc E. The arc E is driven by this force over the ring opening B and it ....
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rotates between the electrodes 20 and 22 until the magnitude of its current has fallen to a predetermined value within the half-wave. At this point, the forces are no longer sufficient to drive the arc over the opening B and the pressure of the quenching gas heated by the arc within the arc chamber has reached a point that the escaping quenching gas forces the ends of the arc into the nozzles 28 and 30 where the arc is then cooled in a particularly effective manner. -The back-up effect, however, prevents the arc base from being blown into the nozzle 28 or 30 for large current values and a correspondingly large arc diameter.
The entrance of the arc base into the respective nozzle shortly ;~
prior to the zero crossing is further aided by an additional loop formation between the current-carrying part of the nozzle Z8, or the nozzle 30 and the -adjacent part G of the arc E. The current parts F and G are shown on Figure 4 in broken lines.
The arc generated between the ends C is acted upon, with the cur- `
rent path assumed above, by magnetic forces which move the arc E of Figure 3 counter-clockwise. These forces are formed by the action of the current loop in conjunction with the effect of the current which flows in the electrodes in the opposite direction and produces the cusp field 42 and 44. These forces K acting on the arc are proportional to the square of the current and are thus large in the vicinity of the peak value of the current half-wave. As long as the magnetic forces are large, the arc in the chamber 2 rotates and in the process heats the quenching medium present therein which may be, for ;
example, sulfur hexafluoride. The pressure in the arc chamber 2 thus rises and a flow of quenching medium through the openings of nozzles 28 and 30 into :.
.
the equalization chambers 10 and 12 is produced. The volume of the arc cham- ~ -ber 2 in conjunction with the diameter and the profile of the nozzles 28 and 30 is chosen so that the pressure reduction in the arc chamber due to the escaping quenching gas takes longer than the respective AC half-wave by which ':~! ' . . ~ ' ! '. ' ' _,' ' .. ':~, .
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,i~ ~ ,, ' the arc, and thus the pressure, ~as produced. The flow through the nozzles 28 and 30 thus lasts beyond the zero crossing of the current. AccoTdingly, the bases entering into the nozzles and the adjacent parts of the arc are cooled by the nozzle flow only immediately prior to the zero crossing of the arc. The nozzle flow from a practical standpoint has almost no influence on the arc as long as the current is still large, i.e., in the vicinity of the peak value of the current half-way.
When the current approaches its zero crossing near the end of the half-waye, the magnetic driving forces K on the arc decline relatively quick-ly and no longer can drive the arc over the insulation gap B. This occursat some predetermined current value. At that point, a base of the arc E is driven into the respective nozzles 28 or 30. A particularly advantageous further embodiment of the quenching arrangement of the present lnvention consists in providing the nozzles 28 and 30 with slots, not shown on the figure, which extend radially to the nozzles 28 and 30 in the direction of -their axes. Advantageously, these slots are filled with a heat-resistant .
insulating material. Such slots aid in the formation of loops of current parts F and G shown on Figure 4.
It is further advantageous if the electrodes consist essentially of an electrically conductive material such as copper or also tungsten copper and that the nozzle portion of the electrodes is made of graphite. With such an arrangement, after the base points of the arc have passed to the nozzle area, metal vapor can no longer be generated.
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A further adYantage of the quenching arrangement of the present in~
vention is that only a switching rod or switching tube is required to operate the breaker. A drive with relati~ely low power is thus sufficient since the quenching medium flow need not be generated by external forces. In addition to the illustrated embodiment where the electrodes are an open ring, it may also be advantageous is some cases to make the curvature of the electrodes such that the ends A and C do not form a ring opening but that the ends are always adjacent to an electrode part.
Figure 5 shows a slightly different electrode arrangement. This ~ -illustration which is schematic in form shows an outside housing 58 for the arc chamber along with an electrode 48 having not only a nozzle 50 but addi-tional nozzles 51, 52 and 53 arranged on the circumference of the electrode which is again shaped as an open ring. The diameter of the nozzles 50 through 53 is chosen so that the sum of the discharge cross sections, i.e., the sum of their inside diameters ensures a sufficiently slow pressure reduction in the arc chamber enclosed by the wall 58. The advantage of this configuration with a plurality of nozzles is that as the zero crossing of the current is reached, the arc no longer must travel along the entire circumference of the ring electrode 48 to get into a nozzle. Nozzles can be distributed over the circumference of the electrode 48 in an approximately uniform manner as shown on the figure. Nozzles can also be provided at points of the electrode 48 at which the ring-arc base points have a tendency to remain stationary, for example in the vicinity of deflectors or discontinuities not shown on the figure.
In some cases it may be advantageous to provide in the partition between the arc chamber and an adjacent equalization chamber one or more open- - -ings which permit equalization i.e., a flow of gases back into the arc cham- ~ ~
ber. Such equalization may be necessary if one or more interruption processes ~ -follow after a switching operation with corresponding expansion and discharge 3~ o the ~R~e5 heated b~ the aTc.
, .
'~ In addition to the arc chamber of Figures 1 and 2, an embodiment of the arc chamber as a closed ring cylinder is also possible. Such an arrange-1'~)397~1 :
ment is shown in Figure 6. In the arrangement illustrated thereon, an elec-trode 60 in the form of an open ring is arranged concentrically to chamber walls 62 and 64 such that the arc burns in the direction of the axis of the ring chamber. In this embodiment, the electrode 60 is shown as being provided with a plurality of nozzles designated 70 through 73. An equalization chamber of similar design can be arranged above or below the ring-shaped arc chamber.
In the manner described above, the nozzles 70 to 73 will then open into one ; ~ -of these chambers.
In addition to sulfur hexafluoride SF6 mentioned above, other gase-ous media may also be used for quenching. For example, nitrogen and possibly also air may be used. A liquid quenching medium such as liquid sulfur hexa-fluoride or oil can also be used. An embodiment designed particularly for such a liquid quenching medium is that illustrated by Figure 7. In this arrangement, a cylindrical member 8 is again provided. Within this member, the arc chamber 2 is located in the bottom defined by the bottom 6 and par-tition 4. An equalization chamber 10 is located above the arc chamber 2.
The electrode arrangement is essentially the same as that of Figure 1 except that herein only the nozzle 28 is provided, the electrode 22 having, instead of a nozz}e, a pressure or spring contact 128 in the bottom of the arrange- ~ ;~
ment. Liquid quenching medium 150 is placed in the bottom of the arc chamber
This inYention relates to a method of quenching an arc in an alternating current circuit breaker having an arc chamber in which the rotating arc is blasted by a quenching medium. Circuit breakers of this kind are pre~
ferably used in medium- and high-tension plants, in particular carrying a supply voltage exceeding 1000 V.
It is generally known that medium- and high-tension circuit breakers for alternating current extinguish at the zero-crossing point of the current. In a compressed gas circuit breaker a locally restricted circuit-breaking arc is subjected to the flow of a quenching gas, whereas in a circuit breaker with a rotating arc the arc is quenched by imparting to it a rapid movement in a stationary gas, prefer-ably a quenching gas, in particular sulfur hexafluoride SF6.
Circuit breakers with a rotating arc do not require pressure .. .. .
gradient in the quenching gas, German Patent 646,031 discloses the quenching of an arc which rotates in a quenching medium inside an arc chamber. The arc is driven by an electromagnetic field into ;
, 20 a pressurized flow of a quenching medium flowing out of the J
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1 .~ ' . . ' : ' !~
:
~39~81 chamber and the arc is rotated in this flowing medium by means of another electromagnetic field. One of the low ends of the arc is driven by the electrodynamic effect of a current loop into a tubular contact. The arc is rotated inside that tube and blasted by the flowing quench- -ing mediu~. The cross-section of the flow, defined by the internal width of the tubular contact must, therefore, be of a magnitude sufficient to permit rotation of the arc within the opening.
Although these prior art methodsand apparatus work reasonably well, there is a need for improved methods :
of arc quenching due to various deficiencies. Prior to summarizing the present invention, a discussion of the oper- .
ation of gas flow breakers which operation is helpful in un-derstanding the present invention will be given. - :' -In what are referred to as gas flow breakers, i,e., high capacity circuit breakers using flowing gas as a quenching medium, in which the arc burns in nozzle arrange-ments, the switching capacity is heavily influenced by what '~
: ~ .
~ ,, ' i~
j 2 ~.
1~39781 is referred to as back-up effect. Back-up effect is a certain interaction between the quenching gas flow and the arc. In a gas flow breaker the arc burns between two contacts, at least one of which is generally shaped as a tubular contact and forms at the same time a nozzle for thé gas flow. However, it is also possible for the contacts to be preceded by a separate nozzle.
The ~asic characteristic of all these arrangements is that the arc must burn through a hollow space. The hollow space may be cylindrical, conical or Laval-tube shape and may be of different length. The quenching medium must flow through this hollow space forming the nozzle or acting as a nozzle. The quenching medium flow will be impeded by an arc therein. Using simple model concepts, two zones can be distinguished within the nozzle, and inner hot zone with low density and an outer cold zone with high density. The inner zone is formed by the arc while the major portion of the total mass passing through the nozzle flows through the outer cold zone. The thicker tha arc becomes, the wider the hot zone becomes. This happens at the expense of the cold outer zone. As a result, with increasing arc thickness, the mass flow through the nozzle teclines. If the arc completely fills the nozzle cross-section, mass ; flow is minimal.
,~ , Thus, flow resistance in the nozzle increases as a function of the power of the arc. At the same time, the mass flow through the nozzle decreases :t ~ .
~ as a function of the temperature. The removal of the gas heated in the quench-`t~. ing chamber for the duration of the arc requires a certain amount of time, ~ ~ ~ particularly where large currents are being switched. Furthermore, the gas 3 flow adjusts itself only subsequently with a time delay because of the mass inertia. In an AC circuit breaker, the arc current varies in accordance with the sinusoidal waveform of the current half-waves. In interrupting a large current, particularly a short-circuit current, the effects mentioned above occur in the vicinity of the current maximum.
f~
With increasing cooling-down of the arc, a radial gas flow inward occurs and thereby a corresponding increase in density. An additional annular _ . ,~ : .
1~39781 c~oss sectlon is thus m~de aYailable fo~ the gas flow. At the zero crossing of the current, the undlsturbed steady~state flow which depends only on the pressure is not yet reestablished but is reduced by a predetermined amount. This flow reduction impedes the cooling of the arc and the development of a temper-ature distribution favorable for quenching at the important time interval just prior to the zero crossing.
The reduced cooling effect in dependence on the decreasing mass flow has a consequence that the power released in the quenching chamber cannot be removed by the quenching medium. One result of this is a large pressure increase in the quenching chamber. The pressure increase can lead not only to a reduction of the inflow from the high-pressure part of the circuit breaker, but even to a reversal of the flow direc-.
tion. Through such a reverse flow, hot gas can get into the supply canals. If with a then decreasing magnitude of the current, the gas flow resumes in the desired direction, quenching medium which has already been heated and which may be contamin-ated with metal vapor from the electrodes flows first into the 2Q quenching arrangement. Because of these effects, designs which largely suppress the back-up effect using the special measures ;
have been developed. Typical are the measured disclosed in the document ETZ-A, vol. 90, no. 26, pages 711 to 714 tl969) where ETZ is an abbreviation of Elektro-technische Zeitung).
~ In gas flow breakers, the back-up effect is prevented primarily y .~ .
!: ~4~ ~-by making the discharge openings of the nozzles relatlvely large, in accordance with the power to be interrupted The back-up effect which occurs in conjunction with the known quenching of an arc by rotation between elec-trodes arranged parallel to each other can lead to a particular-ly advantageous quenching effect. Thus, the present invention essentially comprises using the arc to generate during its rotation an overpressure due to heating of the quenching --medium which is maintained beyond the zero crossing of the AC current and which thereby results in a gas flow of the quenching medium which is used for blasting the arc in a nozzle. With the method of the present invention, a back-up effect is thus generated in order to bring about, during the current half-wave, a pressure build-up in the arc chamber, which then results in a flow of the quenching medium through the nozzles.
Contrary to the known gas flow breakers, intensive I flow cooling is achieved only in the immediate vicinity of ! the time of the current zero crossing, i.e., only at that , 20 time is the arc in the vicinity of the nozzle. It has i - .. .
, :
~` " ', :
1039~78~
been d~scovered that it is adYantageous that the arc be cooled as little as poss~le during the rotation phase, in ~ ;
order to keep the power conYersion as low as possible. For this reason, particularly fast rotation is not required. ;
The rotation of the arc is used primarily to reduce burn-off of the electrodes and to heat the quenching medium in the arc chamber as uniformly as possible. -When the current is being switched off, the arc can be drawn from one electrode to the other in a simple fashion using a switching bar, which in the closed condition protrudes through the nozzles disposed opposite each other in the arc quenching chamber. Thus, a switching rod movable in its ~;
length-wise direction is provided for operating the breaker.
Similarly, a switching tube may also be used. ~or establish-ing good contact, at least one of the nozzles can be equipped ~ with spring contacts or a pressure contact device of well ¦~ ~ known design.
¦~ In some cases, a single equalization chamber arranged ¦ ~ above or below a cylindrical arc-quenching chamber may be ¦~ 20 suficient, In such an arrangement, quenching gas 10ws from one side of the chamber through a nozzle and the arc is accord-ingly influenced by the flow only on one side. With such an arrangement of the switching apparatus, the end of the other electrode opposite the nozzle can advantageously be provided ` ~ with a pressure or finger contact arrangement of known design.
The end of the switching rod is then connected with this contact arrangement when the breaker is closed. The switching~tube or rod movably arranged in one or two nozzles ;
` ~ ~ can additionally be guided b~ a sliding contact disposed in the 30- equalizatlon chamber. In an arrangement where two equalization ~6 ~ r ~1)39781 ~
chambers are used, such a sliding contact can further be provided in addition to the second equalization chamber.
According to a broad aspect of the present invention there is pro- ~-vided apparatus for quenching a rotating electric AC arc of high current intensity having an arc chamber wherein the arc heats a quenching medium which is adapted to flow off at a predetermined over-pressure through at least one opening in an equalization chamber, characterized in that the open-ing has the configuration of a nozzle disposed in such a fashion that at least during the quenching phase the arc fires through this nozzle and in that the dimensions of the nozzle are selected in such a manner that the ~
over-pressure produced in the arc chamber is maintained beyond the zero ~;
passage of the AC current.
In a disclosed embodiment of the invention, electrodes which con-tain discharge nozzles in several places for conducting the quenching medium from the arc chamber to the equalization chamber are provided. The addition-al nozzles are disposed at points of the electrodes where it can be expected that the base points of the arc will remain stationary for small magnitudes of the current due to the greater curvature or an insulating interruption.
In such a case, the magnetic driving forces will no longer be sufficient to move the base points away from these electrode parts. The sum of the inside nozzle cross sections is chosen such that the back-up effect, which is ad-vantageous for the generation of the flow, can still take place.
In each of the disclosed arrangements, it is advantageous to embed the electrotes of conductive material along with at least one nozzle in slots of insulating plates or walls of the arc chamber. This prevents the highly curved, voltage-carrying edges from projecting into the arc chamber a~d improves the dielectric strength of the chamber considerably.
,, - . . .
In the equalization chambers, additional magnetic blasting coils ~"~ will preferably be provided. The blasting coils are connected to the elec-trodes and their current leads -~ .. . . .
~ C ' ~ ~
:.' ~
1~J39781 in such a manner that they are bridged, i.e., electrically , shorted, by the switching rod or the switching tube when the breaker is closed. Thus, they a~re in the circuit only during the switching process. ~he blasting coils may further be associatPd with at least one shorted turn which produces a phase shift of the magnetic field with respect ;
to the arc current. As a result, the driYing force acting on the arc current will remain relatively large even shortly prior to the zero crossing of the current.
For limiting the current, electric resistors which are switched into the circuit upon operation of the breaker and thereby limit the current to be interrupted, e.g., a short-circuit current, to a low Yalue can be included ;
in the equalization chambers in addition to or instead of ~ the coils.
j A particular adYantage of the apparatus disclosed is that seYeral switching deYices can be connected in series in a simplb manner with a common driYe associated with the switching rod of the indiyidual switchiDg deYices.
~ 20 In addition to a gaseous quenching medium such I as sulfur hexafluoride, the quenching device according to ,1 .
.
~.~: .
. .
.
1~39781 the present invention can al50 be operated with a liquid quench-ing medium such as oil. In such an embodiment, the oil evapor-ates due to the arc and the oil vapor is used for blasting at least one of the arc bases. In such a case, it i5 advantageous to provide the equalization chambers with val~es which allow the decomposition products to discha~ge to the outside.
A particularly advantageous embodiment of the quench-ing arrangement using a liquid quenching medium is obtained through the use of liquid sulfur hexafluoride SF6. Liquid SF
has a vapor pressure of 21 atmg at 20C and still about 5.1 atm abs at -30C. Thus, at normal ambient temperature, e.g., between 0 and 30C, an SF~ gas atmosphere of 13 to 27 atm abs in a switching chamber partially filled wi~h liquid sulfur hexa-fluoride SF6 is present. This causes a substantial increase of the dielectric strength as compared to a breaker operated only with a pure SP6 gas atmosphere of about 5 to 7 atm abs.
Since the decomposition products of sulfur hexafluoride recom-bine to again form sulfur hexafluoride upon cooling down, a discharge of the decomposition products to the outside is not necessary where this is used as the quenching medium. This is a great advantage, particularly for an installation in an encapsulated system.
Figure 1 is a cross-sectional view of a first ~ embodiment of a quenching arrangement having two equalization ¦ chambers.
~,~ Figure 2 is a plan view partially in cross-section I illustrating a type of electrode which can be used in the `1 ' .
''~ ;~''' ., , ., ~ , .. ~ .-. .. , .. . . ,. ,,. ,. ,, , .. , . , . . : , .. .
1~39781 : ~:
embodiment of Figure 1.
Figure 3 is a perspective view illustrating current flow through the electrode of Figure 2 and the magnetic -fields generated thereby. -~
Figure 4 is a cross-sectional view of a nozzle electrode of Figure 1 illustrating current flow therethrough.
Figure 5 is a plan view illustrating another type ~ -~
of electrode which may be used.
Figure 6 illustrates a still further type of elec-trode.
Figure 7 is a similar view of an arrangement with a single equalization chamber which arrangement is particularly adapted for use with a liquid quenching medium.
A first embodiment of a quenching arrangement for carrying out the method of the present invention is illustrated on Figure 1. An essentially cylindrically shaped member 8 ; having a top cover 14 is provided. Centrally located within this cylindrical structure is a quenching chamber 2 defined by a top partition 4 and a bottom partition 6 along with the ;
cylindrical side walls of the cylindrical member 8. The space ;
between the partition 4 and the top 14 forms a first equaliza-tion chamber. A partition 16 along with the partition 6 forms a second equalization chamber 12. As illustrated, the equaliz-;~ ation chamber 10 is above the quenching chamber 2 and the equalization chamber 12 below the quenching chamber 2 The ~ walls of the chambers including the cylindrical wall 8, the ~~ .
~ top 14, bottom 16 and partitions 4 and 6 may advantageously .~
~; be made of a-heat resistant insulating material, such as ceramic or -,; :'.. . :, '~
~1 :~t~, r ~ ~
1039781 ~
plastic. At the inside surface of the partition 4 of the arc chamber 2 and at its bottom partition 6, also on the inside, are arranged re~pective elec-trodes 20 and 22. One end of the electrode 20 is connected with an electri-cal lead 24 and one end of the electrode 22 with an electrical lead 26. The other end of the electrode 20 is designed as a nozzle 28 and that of the electrode 22 as a nozzle 30. The nozzles 28 and 30 form respective openings in the partitions 4 and 6. A switching rod 32 having an outside diameter matching the inside diameter of nozzles 28 and 30, protrudes through both nozzles, establishing the electrical connection between the electrodes 20 and 22. The switching rod can be moved along its axis by a drive, not shown. It is brought through a corresponding opening in the bottom 16 of the lower equalization chamber 12 and will preferably be guided in an additional sliding contact 34 arranged at the bottom partition 16. As shown, it can be electri-cally connected with the lead 26 along with being connected to a current sup-ply line 36. The two equalization chambers 10 and 12 can also have therein a magnet coil. Shown is a magnet coil 38 in chamber 10 and a magnet coil 40 in chamber 12. These produce a magnetic blasting field for the arc which is drawn between the electrodes 20 and 22 using the switching rod 32. The blast-I ing coils 38 and 40, whose electrical conductor connections are not shown in t 20 the figure, are connected electrically in series and in magnetic opposition.
At least one short-circuited turn, also not shown on the figure, can be i~
~ associated with each of the blasting coils 38 and 40 to cause, in a well known ~ fashion, a phase shift of the magnetic field of the blasting coil with res-pect to the arc current producing the field. These short-circuit turns may be arranged, for example, directly at the coils 38 and 40 or may partially sur-round the coils. With such an arrangement, they will have a particularly close coupling with the coils.
~etween the arc chamber 2 and the equalization chambers 10 and 12, tl~ respective chec~ valves 18 and 19 are provided. These are adjusted so that ' 30 they open only upon exceeding a predetermined maximum pressure in the arc .~. ' . ' , .
. : ' - - - - ... , .. , . ',: , ~39781 :
chamber 2. They thereby make possible a reduction of the pressure by providing openings in addition to the nozzles. Also shown on Figure 1 are safety valves 37 and 39 in the wall 8 at the chambers 10 and 12 respectively. These safety valves which vent to the outside are set to a predetermined maximum pressure and may, for exampleJ be spring valves or burst diaphragms. These safety devices prevent an explosion of the switching device if the current being in-terrupted assumes values which cannot be interrupted by the circuit breaker.
Either one or both of the safety valves 37 and 39 may be advantageously in-cluded.
As is evident from the cross-sectional plan view through the arc chamber 2 as shown on Figure 2, the electrode 20 is an open ring electrode which has an approximately uniform distance from the chamber wall 8 and whose ends A and C form an opening B in the ring. The end C has a larger cross section with its inner opening 29 forming the nozzle whose cross-sectional profile is laid out for aerodynamic acceleration and preferably may have the profile of a Laval tube.
During a half-wave of the operating current, which as illustrated on Figure 3, flows through the lead 26 along with electrode 22 in the direction indicated by the arrow, an arc E is drawn between the ends C of the electrodes -- 20 and 22 as the switching rod 32 is moved downward~ In the electrode 20, the current flows in the opposite direction, also as indicated by arrows on Figure 3, and leaves the quenching arrangement through the lead 24.
With the directions of current indicated, the two ring-shaped electrodes 20 and 22 form what is referred to as a cusp field designated by 42 and 44 and shown in dot-dash lines on the figure. The cusp field has a rad-ial component which generates a force K acting on the arc E in the tangential direction in the space between the electrodes 20 and 22. The arc is also ! ~ driven by the action of its own electromagnetic force. The latter is produced by the loop formation of the electrode parts adjacent to the ends C with the arc E. The arc E is driven by this force over the ring opening B and it ....
.::
rotates between the electrodes 20 and 22 until the magnitude of its current has fallen to a predetermined value within the half-wave. At this point, the forces are no longer sufficient to drive the arc over the opening B and the pressure of the quenching gas heated by the arc within the arc chamber has reached a point that the escaping quenching gas forces the ends of the arc into the nozzles 28 and 30 where the arc is then cooled in a particularly effective manner. -The back-up effect, however, prevents the arc base from being blown into the nozzle 28 or 30 for large current values and a correspondingly large arc diameter.
The entrance of the arc base into the respective nozzle shortly ;~
prior to the zero crossing is further aided by an additional loop formation between the current-carrying part of the nozzle Z8, or the nozzle 30 and the -adjacent part G of the arc E. The current parts F and G are shown on Figure 4 in broken lines.
The arc generated between the ends C is acted upon, with the cur- `
rent path assumed above, by magnetic forces which move the arc E of Figure 3 counter-clockwise. These forces are formed by the action of the current loop in conjunction with the effect of the current which flows in the electrodes in the opposite direction and produces the cusp field 42 and 44. These forces K acting on the arc are proportional to the square of the current and are thus large in the vicinity of the peak value of the current half-wave. As long as the magnetic forces are large, the arc in the chamber 2 rotates and in the process heats the quenching medium present therein which may be, for ;
example, sulfur hexafluoride. The pressure in the arc chamber 2 thus rises and a flow of quenching medium through the openings of nozzles 28 and 30 into :.
.
the equalization chambers 10 and 12 is produced. The volume of the arc cham- ~ -ber 2 in conjunction with the diameter and the profile of the nozzles 28 and 30 is chosen so that the pressure reduction in the arc chamber due to the escaping quenching gas takes longer than the respective AC half-wave by which ':~! ' . . ~ ' ! '. ' ' _,' ' .. ':~, .
- 13 - - ;
.. ' .~ ' .
,i~ ~ ,, ' the arc, and thus the pressure, ~as produced. The flow through the nozzles 28 and 30 thus lasts beyond the zero crossing of the current. AccoTdingly, the bases entering into the nozzles and the adjacent parts of the arc are cooled by the nozzle flow only immediately prior to the zero crossing of the arc. The nozzle flow from a practical standpoint has almost no influence on the arc as long as the current is still large, i.e., in the vicinity of the peak value of the current half-way.
When the current approaches its zero crossing near the end of the half-waye, the magnetic driving forces K on the arc decline relatively quick-ly and no longer can drive the arc over the insulation gap B. This occursat some predetermined current value. At that point, a base of the arc E is driven into the respective nozzles 28 or 30. A particularly advantageous further embodiment of the quenching arrangement of the present lnvention consists in providing the nozzles 28 and 30 with slots, not shown on the figure, which extend radially to the nozzles 28 and 30 in the direction of -their axes. Advantageously, these slots are filled with a heat-resistant .
insulating material. Such slots aid in the formation of loops of current parts F and G shown on Figure 4.
It is further advantageous if the electrodes consist essentially of an electrically conductive material such as copper or also tungsten copper and that the nozzle portion of the electrodes is made of graphite. With such an arrangement, after the base points of the arc have passed to the nozzle area, metal vapor can no longer be generated.
1 . , ~ 14-! ~ .
A further adYantage of the quenching arrangement of the present in~
vention is that only a switching rod or switching tube is required to operate the breaker. A drive with relati~ely low power is thus sufficient since the quenching medium flow need not be generated by external forces. In addition to the illustrated embodiment where the electrodes are an open ring, it may also be advantageous is some cases to make the curvature of the electrodes such that the ends A and C do not form a ring opening but that the ends are always adjacent to an electrode part.
Figure 5 shows a slightly different electrode arrangement. This ~ -illustration which is schematic in form shows an outside housing 58 for the arc chamber along with an electrode 48 having not only a nozzle 50 but addi-tional nozzles 51, 52 and 53 arranged on the circumference of the electrode which is again shaped as an open ring. The diameter of the nozzles 50 through 53 is chosen so that the sum of the discharge cross sections, i.e., the sum of their inside diameters ensures a sufficiently slow pressure reduction in the arc chamber enclosed by the wall 58. The advantage of this configuration with a plurality of nozzles is that as the zero crossing of the current is reached, the arc no longer must travel along the entire circumference of the ring electrode 48 to get into a nozzle. Nozzles can be distributed over the circumference of the electrode 48 in an approximately uniform manner as shown on the figure. Nozzles can also be provided at points of the electrode 48 at which the ring-arc base points have a tendency to remain stationary, for example in the vicinity of deflectors or discontinuities not shown on the figure.
In some cases it may be advantageous to provide in the partition between the arc chamber and an adjacent equalization chamber one or more open- - -ings which permit equalization i.e., a flow of gases back into the arc cham- ~ ~
ber. Such equalization may be necessary if one or more interruption processes ~ -follow after a switching operation with corresponding expansion and discharge 3~ o the ~R~e5 heated b~ the aTc.
, .
'~ In addition to the arc chamber of Figures 1 and 2, an embodiment of the arc chamber as a closed ring cylinder is also possible. Such an arrange-1'~)397~1 :
ment is shown in Figure 6. In the arrangement illustrated thereon, an elec-trode 60 in the form of an open ring is arranged concentrically to chamber walls 62 and 64 such that the arc burns in the direction of the axis of the ring chamber. In this embodiment, the electrode 60 is shown as being provided with a plurality of nozzles designated 70 through 73. An equalization chamber of similar design can be arranged above or below the ring-shaped arc chamber.
In the manner described above, the nozzles 70 to 73 will then open into one ; ~ -of these chambers.
In addition to sulfur hexafluoride SF6 mentioned above, other gase-ous media may also be used for quenching. For example, nitrogen and possibly also air may be used. A liquid quenching medium such as liquid sulfur hexa-fluoride or oil can also be used. An embodiment designed particularly for such a liquid quenching medium is that illustrated by Figure 7. In this arrangement, a cylindrical member 8 is again provided. Within this member, the arc chamber 2 is located in the bottom defined by the bottom 6 and par-tition 4. An equalization chamber 10 is located above the arc chamber 2.
The electrode arrangement is essentially the same as that of Figure 1 except that herein only the nozzle 28 is provided, the electrode 22 having, instead of a nozz}e, a pressure or spring contact 128 in the bottom of the arrange- ~ ;~
ment. Liquid quenching medium 150 is placed in the bottom of the arc chamber
2. This liquid quenching medium 150 is partially evaporated by the arc which is drawn when the switching rod 32 is moved from the contact 128 up-ward. The arc is drawn between the contact 128 and the nozzle 28. The k ; evaporated quenching medium flows through the nozzle 28 into the equalization chamber 10. After the switching operation the evaporated quenching medium collects at the bottom of the equalization chamber 10. The return of the condensed quenching medium from the equalization chamber 10 to the arc chamber 2 can be facilitated by at least one additional opening 152.
In order to discharge the decomposition products of the quenching medium, at least one check valve 154 located in the wall 8 of the quenching .~ .
lj~ -16-1 ` ~
~ C .~.,"'' ' 1~:)39781 ~ ~
arrangement can be proyided~ The yalye will be adjusted to open at a pre-determined adjustable oveTpressure.
Because of their particularly compact and space-saving type of construction, the quenching arrangements of the present invention are parti~
cularly well suited for installation in partially or completely encapsulated switching systems.
Thus, an improved method of arc quenching and a number of embodi-ments for carrying out that method have been disclosed. Although a particular method and particular embodiments haye been illustrated and described, it will be obYious to those skilled in the art that Yarious modifications may be made without departing from the spirit of the in~ention which is intended to be limit-d s~lely by the appended claiDs.
~'' '"' ' '.~ ~'.":' ,:
,, ..,.. :..
, ;'.,' ;
' 1 . ~' , ~ ', ' '., ',' '~ ' '"' ' l, -17- ~ :
;, ,;~.. ~ . . :.
In order to discharge the decomposition products of the quenching medium, at least one check valve 154 located in the wall 8 of the quenching .~ .
lj~ -16-1 ` ~
~ C .~.,"'' ' 1~:)39781 ~ ~
arrangement can be proyided~ The yalye will be adjusted to open at a pre-determined adjustable oveTpressure.
Because of their particularly compact and space-saving type of construction, the quenching arrangements of the present invention are parti~
cularly well suited for installation in partially or completely encapsulated switching systems.
Thus, an improved method of arc quenching and a number of embodi-ments for carrying out that method have been disclosed. Although a particular method and particular embodiments haye been illustrated and described, it will be obYious to those skilled in the art that Yarious modifications may be made without departing from the spirit of the in~ention which is intended to be limit-d s~lely by the appended claiDs.
~'' '"' ' '.~ ~'.":' ,:
,, ..,.. :..
, ;'.,' ;
' 1 . ~' , ~ ', ' '., ',' '~ ' '"' ' l, -17- ~ :
;, ,;~.. ~ . . :.
Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for quenching a rotating electric AC arc of high current intensity having an arc chamber wherein the arc heats a quenching medium which is adapted to flow off at a predetermined over-pressure through at least one opening in an equalization chamber, characterized in that the open-ing has the configuration of a nozzle disposed in such a fashion that at least during the quenching phase the arc fires through this nozzle and in that the dimensions of the nozzle are selected in such a manner that the over-pressure produced in the arc chamber is maintained beyond the zero passage of the AC current.
2. Apparatus according to claim 1, in which in the arc chamber two open ended annular electrodes are coaxially disposed parallel to one another, one end of the electrodes being connected with an electrical lead and the other end of one of the electrodes containing the nozzle.
3. Apparatus according to claim 2, in which other end of the other annular electrode has the configuration of a contact cooperating with an end of a switching rod which is adapted to extend through the nozzle into the equalization chamber and which is movable in an axial direction.
4. Apparatus according to claim 1, in which in the arc chamber two open ended annular electrodes are coaxially disposed parallel to one another, one end of the electrodes being connected with a lead and the other end of each annular electrode having the configuration of a nozzle, the electrodes being interconnected through a switching rod which is adapted to be moved in an axial direction into registry with the nozzles.
5. Apparatus according to claim 4, in which at least one of the nozzles has the configuration of a contact cooperating with an end of a switching rod which is adapted to extend through the nozzle into the equalization chamber and which is movable in an axial direction.
6. Apparatus according to any one of claims 3 to 5, in which the switching rod additionally passes through at least one annular contact dis-posed in the equalization chamber and adapted to slide relative thereto.
7. Apparatus according to claim 1, characterized in that in the arc chamber there are two open ended annular electrodes disposed parallel to one another in coaxial fashion, one end of the electrodes being connected with a lead and the annular electrodes comprise a plurality of nozzles.
8. Apparatus according to claim 2, in which the annular electrodes are made of different material from that of the nozzle.
9. Apparatus according to claim 8, in which the electrodes are made from metal and the nozzle is made from graphite.
10. Apparatus according to claim 1, in which a liquid quenching medium is provided in the arc chamber.
11. Apparatus according to claim 10, in which the quenching medium provided is liquid sulfuric hexafluoride (SF6).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA204,921A CA1039781A (en) | 1974-07-17 | 1974-07-17 | Multi-chamber arc quenching device with nozzle-chaped contacts |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA204,921A CA1039781A (en) | 1974-07-17 | 1974-07-17 | Multi-chamber arc quenching device with nozzle-chaped contacts |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1039781A true CA1039781A (en) | 1978-10-03 |
Family
ID=4100676
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA204,921A Expired CA1039781A (en) | 1974-07-17 | 1974-07-17 | Multi-chamber arc quenching device with nozzle-chaped contacts |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1039781A (en) |
-
1974
- 1974-07-17 CA CA204,921A patent/CA1039781A/en not_active Expired
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